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Lecture 13

lecture 13 notes from prof.Barrett

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Department
Biology
Course Code
BIO120H1
Professor
Spencer Barrett

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Lecture 13: Darwin’s big idea and how it changed biology The theory of evolution Ÿ Living things change gradually from one from into another over time Ÿ Involves 2 controversial ideals ○ Concept of a changing universe (constantly changing) v Replaced view of a static world ○ A phenomenon with no purpose (cannot stop evolution, no purpose) adaptation is consequences of evolution v Replaced view that the causes of all phenomena had to have a purpose v Just like the concept of gravity in physics, no purpose to it , just consequences. Jean-Baptiste de Lamarck Ÿ First used the term evolution Ÿ Propose a causal mechanism – the inheritance of acquired characters (wrong!) ○ Simplest forms evolve directly to complex form ○ Linear evolution (wrong because evolution is actually branched) Ÿ The giraffe’s neck: Lamarck’s example for the inheritance of acquired characters ○ Progressive increase in neck during the life timeof individuals is passed on to offspring. Ÿ Wrong because if father got tan, his offspring will not be tan.... Why is Lamarck wrong? August Weisman Germ Plasm theory Ÿ Inheritance only by germ cells (gametes), somatic cells (soma) do not function as agents of heredity. Ÿ Thus genetic information cannot pass from soma to gametes and onto next generation Ÿ Genetic information flows only in one direction. DNA→protein. NEVER REVERSE Charles Darwin & Alfred Russell Wallace co-discover the chief mechanism of evolution Natural selection Ÿ The key publication was a co-authored paper done by Wallace& Darwin, published in London Ÿ Wallace idealize Darwin, he read Darwin's first book (travel catalog). Realize that he can make a living by traveling the world and collect specimen of plants and animals. Ÿ Turn out that the upper-class England love to have stuffed animals in their wall. Ÿ While Wallace was colleting specimen, it give him the idea of evolution. The origin of species Ÿ Darwin wrote dozens of book in different areas (for ex. Sexual selection, evolutionary psychology) Ÿ Events leading up to the publication of "the origin of species" ○ After return from Beagle (he was a ship naturalist, he is a careful note taker) 20 years taken up with accumulation of evidence for thetheory of evolution ○ 1844: wrote but did not publish an essay on natural selection (living in Down House) ○ 1856: began work on natural selection book ○ June 1858: received "On the tendency of varieties to depart indefinitely from the original type" by A.R. Wallace ○ July 1858: Linnean Society presentation in London of Darwin-Wallace paper ○ 1859: publication of "The origin of species by means of natural selection or the preservation of favored races in the struggle for life" Why is this book so important? Two key components: 1.Macroevolution concept: As a tree of life, that all organisms have descended with modification from common ancestors. 2.Microevolution concept: The major agent of modification is natural selection operating on variation among individuals. Relationship between evo
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